Petrological and geochemical characteristics, distribution, tectonic settings and forming conditions of adakites are summarized in this paper on the basis of related papers published in the past 20 years. As high_Al (Al2O3>15%) felsic rocks with high Sr content (400×10-6~2 000×10-6) and low Y and Yb content (Y≤18×10-6, Yb≤1.9×10-6), high La/Yb, Sr/Y and low K2O / Na2O (<0.5)ratios,adakites are character- ized by strongly fractionated REE and absence of Eu negative anomaly, resembling Archean high-Al TTG. Cenozoic adakites are exclusively distributed in circum-Pacific regions, while ancient adakites are also found in some orogenic belts. Most adakites were produced by patial melting of young (<25 Ma) and hot subducting oceanic crust, but some might have been produced by melting of underplated basalts, or delamination of lower continental crust. Generally, the melting residues are considered to be eclogites, garnet-bearing amphibolites, or occasionally granulites. Petrological experiments and geological evidence indicate that adakitic rocks could be formed in a relatively wide pressure range (1.0~2.6 GPa).